CAMBRIDGE, Mass. — Just over one week from the Head of the Charles, the City of Cambridge is sending out an alert about an algae bloom in the Charles River.
According to city officials, the alga bloom is downstream from the River Street and Cambridge Street bridge.
Residents should not eat fish caught in the river or allow their pets to drink the water.
The health advisory was first issued by the Massachusetts Department of Public Health (DPH) in late July 2025, but since the first advisory was issued, the cyanobacteria bloom has expanded upstream, officials say.
City officials will lift the advisory after two rounds of samples collected a week apart indicate that algae is no longer at unsafe levels.
The Head of the Charles Regatta is set for October 17th through the 19th.
The world-renowned rowing event brings thousands of people to the area from all over the world.
This will be the regatta’s 60th anniversary.
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